The present invention relates to rare earth oxysulfide particulate materials, and particularly relates to terbium-activated rare earth oxysulfide phosphors exhibiting an enhanced blue emission as well as a method for producing such enhancement.
Rare earth oxysulfides have long been recognized in the art as valuable luminescent materials. These phosphors are in the form of a solid solution having a matrix of the rare earth oxysulfide compound with a small amount of an activator or dopant dispersed throughout the matrix. The activator normally is also a rare earth element.
Among such rare earth activated rare earth oxysulfides is the blue-green emitting terbium-activated rare earth oxysulfide having the nominal formula: EQU M.sub.2-x O.sub.2 S:xTb (1)
where x is 0.001 to 0.2. The matrix rare earth metal element (M in Formula 1) in this phosphor typically is gadolinium, lanthanum, yttrium, scandium, lutetium, or mixtures of these metals.
The phosphor is useful, e.g., in the field of x-ray intensifier screens. However, the spectral sensitivity of the x-ray film does not always precisely match the phosphor emission. Thus, it would be desirable to have the capability to adjust the green and/or blue emission of the phosphor to tailor the phosphor emission to the spectral sensitivity of the x-ray film.
Accordingly, it is an object of the present invention to provide a terbium-activated rare earth oxysulfide phosphor which overcomes the disadvantages of the prior art.
It is another object of the invention to provide a terbium-activated rare earth oxysulfide phosphor in which the blue emission of the phosphor is enhanced.
It is yet another object of the invention to provide a terbium-activated rare earth oxysulfide phosphor in which the phosphor emission can be tailored to match to the spectral sensitivity of a particular x-ray film.
It is still another object of the invention to provide a method of enhancing the blue emission of a terbium-activated rare earth oxysulfide phosphor.